Lab Notes · 6 min read
These are the questions I have been asked most over twenty years of coaching. Is strength training or cardio more important for fat loss? For living longer? Which one is safer? Here are my answers, with the research behind each one.
Start with what strength training does. It builds muscle. Muscle is metabolically active tissue, so it raises how much energy you burn during every activity, including cardio, and at rest.
That makes muscle a prerequisite for burning a lot of calories. It also decides what kind of weight you lose. In a trial where older adults all followed the same diet, the group that did aerobic exercise lost more than twice as much lean mass as the group that lifted. Both groups lost about the same amount of weight. The lifting group kept more of its muscle.
Villareal et al., New England Journal of Medicine 2017;376(20):1943–1955
So for fat loss, strength training comes first. Losing weight is easy to measure on a scale. Losing fat while keeping muscle is the result that actually changes your body, and what kind of weight you lose is decided by whether you lifted while you lost it.
For years the research made no sense. Lighter people were supposed to live longer and they did not. When researchers stopped weighing people and measured what their bodies were made of, the answer was muscle. The people carrying the most muscle for their height lived the longest, whatever the scale said about them.
Srikanthan & Karlamangla, American Journal of Medicine 2014;127(6):547–553
That is not an excuse to be overweight. It means the amount of muscle you carry matters more than how low your body fat goes. Starving yourself to an unrealistic body-fat number takes muscle with it, and muscle is the part that keeps you alive.
The loss of muscle with age is called sarcopenia, and it is a primary driver of age-related decline. Heart disease is the leading cause of death, and people with the highest aerobic capacity, called VO2 max, are the least likely to develop it. Both matter. So the real question is which training builds both.
Strength training does. Done with short rest periods, lifting builds muscle and raises aerobic capacity at the same time. A review of 37 studies in healthy older adults found resistance training by itself raised peak oxygen uptake.
Smart et al., Age and Ageing 2022;51(6):afac143
Cardio raises aerobic capacity and builds very little muscle, and large amounts of it during weight loss cost you muscle. From an efficiency standpoint alone, strength training wins, because one session builds both. How conditioning is built into the lifting is its own Lab Note.
The most common exercise injuries come from overtraining and pattern overload. Pattern overload is the same movement repeated, with the same joints taking the same force, for long stretches of time.
Endurance training is lower intensity and asks for a large amount of work through the same few movement patterns. Strength training is higher intensity and asks for less total work spread across many movement patterns.
I watched this happen. Before The Strength Laboratory I owned a conditioning gym, with circuits and boot camp training. Over a decade I watched clients age into shoulder, knee and back injuries from repeating force they did not have the strength foundation to absorb. The training was applying the strength they already had, over and over, and never building more of it.
That is why I built this gym. Strength is the foundation for every other physical ability, and building it is what protects you from injury.
All of them. Every rep range builds muscle and strength in a different way, so a good program develops all of them. The approach that trains them together is called concurrent periodization, and it is how our training is organised. The three ways we train are on How We Train.
All of this depends on the weight being heavy enough on the day. That is the one thing you cannot feel, and the research on that is clear.
The whole gym runs on an AI-based strength measurement system. Artificial intelligence reads exactly what level of effort you are putting in on every repetition, and it makes sure you are in the right strength-building and muscle-building zone at all times. No junk reps.
Twenty-five minutes. No charge. You walk out with your numbers.
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